Pleasant Hill, MO
Quoted from TRAMD:I know you are being facetious to respond to Phil, but it brings up an interesting thing I've pondered for a while. If we assume that a planet has the "right" conditions for life (at least as far as carbon based lifeforms on Earth): within the correct size, within the correct zone from the correct kind of star, etc...what is the chance that life would "spring up" there? I actually believe it is pretty high. Under the correct conditions, I think the presence of water, a favorable atmosphere, and then abiogenesis given billions of years is fairly likely because given conditions similar to what we have had on Earth, the presence of life is the rule, not the exception. So I guess what I'm saying is that with so many other planets that meet these conditions in the galaxy and universe, there is almost definitely life on MANY other planets.
I read "The Story of Earth: The First 4.5 Billion Years, from Stardust to Living Planet" a year or so ago, and it talks all about how the planet formed, how life formed and progressed to what we know today. It's pretty fascinating stuff. The Great Oxidation Event was a game changer. Oxygen was necessary for life to evolve.
It's highly likely Venus and/or Mars was similar to Earth billions of years ago, and also likely Earth will become like them billions of years from now if we lose our atmosphere. Water vapor is lost to space constantly, so wouldn't that mean at some point there's no water left on Earth? I don't know what replenishes it if anything. Supposedly it was deposited on Earth early on from comets and asteroids, but that's sure a lot of comets to fill the oceans.
